lecture 3 - liver function tests Flashcards
(24 cards)
Multiple Functions of the Liver
Functions: Nutrient uptake, metabolism, energy supply, detoxification, excretion, fighting infections.
Liver Metabolism
Definition: The liver’s role in maintaining plasma levels of metabolites and its involvement in carbohydrate, lipid, amino acid, and protein metabolism.
Metabolic Functions: Carbohydrate metabolism, lipid metabolism, amino acid and protein metabolism, biotransformation.
Carbohydrate-Liver Metabolism
Definition: The liver’s involvement in glucose regulation, glycogen storage, gluconeogenesis, and secretion of glucose.
Processes: Glucose uptake, glycogen storage, gluconeogenesis.
Liver-Lipid Metabolism
Definition: How the liver synthesizes, stores, and transports fatty acids, cholesterol, and other lipids.
Processes: Fatty acid synthesis, cholesterol conversion, bile acid production.
Liver-Amino Acid, Protein Synthesis
Definition: The liver’s role in controlling amino acid levels, protein synthesis, and the breakdown of excess amino acids.
Functions: Control of amino acid levels, protein synthesis, nitrogen conversion to urea.
Albumin
Definition: The most abundant blood protein synthesized by the liver, responsible for maintaining osmotic pressure and binding drugs.
Functions: Osmotic pressure maintenance, drug binding.
Liver Metabolism (Biotransformation)
Definition: How the liver inactivates and converts various substances, including hormones, drugs, and foreign compounds, for excretion.
Processes: Inactivation and conversion of substances, detoxification.
Aminotransferases
Definition: Enzymes involved in loading amino acids onto tRNA’s, including alanine aminotransferase (ALT) and aspartate aminotransferase (AST).
Use as Biomarkers: Indicators of liver damage, especially in acute diseases.
Acute Liver Disease
Definition: Conditions with a rapid decrease in liver function, marked by elevated levels of ALT and AST in the blood.
Indications: Viral infections, inflammation, drug-induced damage, alcohol misuse.
De Ritis Ratio
Definition: The AST/ALT ratio used to differentiate between causes of liver damage.
Interpretation: Various ratios indicate different liver conditions.
Limitations of ALT and AST
Unsuitability for chronic conditions, non-specificity of AST.
Prothrombin Time (PT)
Definition: A measure of how long blood takes to clot, indicative of liver damage when clotting protein synthesis decreases.
Use: Detection of liver damage, especially in chronic conditions.
Metabolism and Excretion of Bilirubin
Definition: The liver’s role in processing bilirubin and its excretion in bile and urine.
Processes: Bilirubin conversion, solubility, excretion in bile, urine coloration.
Jaundice
Definition: Yellowing of the skin and eyes due to increased bilirubin levels, indicating various underlying problems.
Types: Prehepatic, hepatic, post-hepatic; causes and resolution in newborns.
Direct Bilirubin
Definition: Indication of whether bilirubin conjugation or excretion is the issue in jaundice.
Back of Flashcard 15:
Interpretation: High direct bilirubin suggests conjugation is normal, but excretion is problematic.
Cholestatic Tests (ALP)
Definition: Testing for hepatic duct obstruction using alkaline phosphatase (ALP).
Use: Indicator of liver damage or obstruction.
Cholestatic Tests (GGT)
Definition: Testing for cholestasis using gamma glutamyltransferase (GGT).
Use: Differentiating between liver and bone disorders.
Hormones of the Liver
Definition: The liver’s production of hormones like IGF-1, angiotensinogen, and its role in vitamin D synthesis.
Functions: Hormonal regulation, growth, blood pressure, fluid balance.
Vitamin D Synthesis
Definition: The activation of vitamin D in the liver and kidneys through hydroxylation.
Process: Activation of vitamin D from cholesterol precursor.
Detoxification and Secretion of Drugs
Definition: How the liver removes drugs in their original form or modifies them for excretion.
Processes: Drug removal, modification, excretion.
Drug-Induced Liver Damage
Definition: Liver damage caused by substances like paracetamol when detoxification processes are overwhelmed.
Example: Paracetamol-induced acute liver failure.
Metabolism and Storage of Vitamins and Iron
Definition: The liver’s role in handling lipid-soluble vitamins and iron.
Storage: Vitamins (A, D, K, E) and iron storage mechanisms.
Haemochromatosis
Definition: A genetic condition causing iron accumulation in the liver and chronic liver disease.
Causes: HFE gene mutation, iron storage impairment.
Wilson’s Disease
Definition: A rare genetic condition leading to copper accumulation in the liver.
Cause: Impaired copper removal.
